make sure the amd card is in max performance mode and the cpu too as it could be one of the 2 are throttling for pcsx2, Nvidia has max performance mode you can specify per game to keep the card from running lower clocks I sure AMD has something simlar no clue what they call it though. Most games should run full speed at 2-3x native

(GameDB) 9645 games on record (loaded in 126ms)
Path: E:\Giochi\PlayStation 2\pcsx2-5791-windows-x86\plugins\ZZOgl-cg.dll
File is not a valid dynamic library.
Some kinda plugin failure: E:\Giochi\PlayStation 2\pcsx2-5791-windows-x86\plugins\ZZOgl-cg.dll
Path: E:\Giochi\PlayStation 2\pcsx2-5791-windows-x86\plugins\ZZOgl.dll
File is not a valid dynamic library.
Some kinda plugin failure: E:\Giochi\PlayStation 2\pcsx2-5791-windows-x86\plugins\ZZOgl.dll
HLE Notice: ELF does not have a path.